Well… despite the above, the problem is not fixed in general. This morning, Choose Footprint freezes as soon as I type “test”, trying to add a testpoint. Restarting several times, going through the routine
a. Delete two vias (planning to replace them with test points).
b. Click Place/Add Footprint.
c. Type “test” and KiCad is frozen.
However, after some experimentation, I found that if I “save” the PCB layout before “Place/Add Footprint”, then Choose Footprint works o.k.